1. Field of the Invention
The present invention relates to a control method of a centrifuge using a balancer, more particularly a control method that helps the rotor rotate more stably and thus improve the lifetime of the centrifuge by controlling the rotation of the rotor in such a way that the unbalance due to the weight of the samples is compensated accurately and stably when centrifugating the samples loaded in the rotor using the balancer containing balls, a liquid, or both balls and a liquid, thereby reducing the vibration due to the unbalance.
2. Description of the Related Art
In general, by introducing the centrifugal force, instead of gravity, to particles in suspension or substances dissolved in a liquid medium, the sedimentation phenomenon can be accelerated and this process is called centrifugation.
The centrifuge that is used in such a centrifugation is a device employing the principle that the particles of high density contained in suspension tend to migrate to the edge by centrifugal force while the particles of low density tend to gather toward the center, and its general configuration is illustrated in FIGS. 1a and 1b. 
As illustrated in FIGS. 1a and 1b, the general centrifuge has a cushioning member such as vibration-proof rubber or a damper installed to a supporting plate formed at the inner surface of the case, and a bracket or supporting plate installed on the top of said cushioning member. It is a general configuration to install a motor to said bracket or supporting plate, and mount a rotor to the rotating shaft projected from said motor.
This centrifuge uses different types of rotor, depending on its use; a swing-out rotor type rotating perpendicularly to the rotating shaft of the motor and a fixed angle type with cavities rotating at a predetermined angle provided therein.
As the motor rotates at a high speed, exerting a strong centrifugal force to the samples in the bottles or the test tubes which arc disposed inside a horizontal or fixed angle rotor, the centrifuge separates the substances contained in the samples by the difference in the centrifugal forces due to the differences in density. A strong centrifugal force must be exerted to the samples for the separation of the substances in the samples, and in order to apply a strong centrifugal force to the samples, generally the rotor must rotate at a high speed and vibration must not be generated particularly during the high-speed rotation of the rotor.
However, in the process of the high-speed rotation of a centrifuge, vibration is generated by a combination of different causes; deflection motion of the rotating shaft of the motor, whirling motion due to the unbalance of the rotor weight, and other external factors. Among these causes of vibration, the most common cause is the whirling motion due to the unbalance of the rotor weight.
Therefore, for the centrifuge without a balancer, to remove the unbalance that occurs due to the differences in the number or weight of the samples disposed in the rotor, the operator should separately measure the weights of the samples before the operation of centrifugation and remove the differences in weight between the samples before rotating the rotor, which causes an inconvenience in operation.
If the unbalance of weight between the samples occurs, the vibration is generated in the process of centrifugation, causing the problems that the substances in the samples are not separated or even if they had been separated, the separated substances could be remixed with vibration. Furthermore, noise is generated in the process of centrifugation by said vibration.
The centrifuge has a problem in that the action of force and moment due to the unbalance of weight between the samples could cause an excessive vibration in the process of centrifugation, causing a failure of the centrifuge itself. In order to solve those problems of noise and vibration generated in the process of centrifugation, a cushioning member such as a damper or rubber was installed, but had a shortcoming that it did not sufficiently absorb the noise and vibration. Therefore, a centrifuge using a balancer containing balls was suggested in order to solve the problems of noise and vibration caused by the unbalance of weight between the samples.
The ball balancer illustrated in FIGS. 3a and 3b is configured to have compensation material installed inside the case (130) which is formed with a balancing space of an annular shape, wherein a shaft hole (105) through which a rotating shaft of the motor is fixedly coupled is formed in the center of the balancer.
The ball balancer configured as above is provided with balls to an extent of occupying a portion of the balancing space (150) which is formed inside the case (130), and has an advantage that when the rotational speed of the motor (not shown) exceeds the resonant speed, the balls move to an opposite direction to the weight unbalance position, thereby balancing the rotor (not shown) and stabilizing the rotation.
However, it has a drawback that often times an accurate balancing could not be achieved due to various factors such as the vibration characteristics of the system, the initial location of balls, the internal friction of the balancer, etc., and in this ease, the high-speed rotation of the rotor could cause strong vibration and noise, resulting in the safety-related accidents.